Pollen record of climate change during the last deglaciation from the eastern Tibetan Plateau

1.7%) [Fig 3]. Other taxa such as Caprifoliaceae, Thalictrum, Lamiaceae, Spiraeoideae, and Caryophyllaceae were present in a few samples (< 2.0%). Hydrophilous herb pollen (8.9%– 22.8%, mean 15.5%) were mainly Cyperaceae (3.9%–12.6%, mean7.7%), Poaceae (0%–6.7%, mean 2.7%), Polygonum (0%–2.5%, mean 0.8%), Myriophyllum (0.8%–4.6%, mean 2.4%), and Typha (0%–5.7%, mean 1.8%), showing generally high values but decrease in abundance over time. Broad-leaved tree pollen (22.1%–32.0%, mean 27.8%) was relatively stable over time and was dominated by Quercus (3.8%–15.1%, mean 9.7%), Castanea (5.2%–12.6%, mean 9.2%), and Betula (2.5%–6.3%, mean 4.7%), with lesser Ulmus (0%–3.5%, mean 1.4%) and Corylus (0.5%–2.2%, mean 1.5%). Liquidambar and Juglans were sporadically present. Conifer pollen (3.1%–10.5%, mean 6.8%) was dominated by Pinus (1.6%–7.8%, mean 4.6%). Abies and Picea pollen (0%–5.9%, mean 1.9%) was present at low and highly variable values. Fern spores and algae were dominated by Pediastrum (3.2%–9.4%, mean 4.8%) and mono- lete spores (0.5%–7.7%, mean 3.8%), and they decreased through time from 17.9% to 5.1% with a mean of 10.9%. Polypodium (0%–1.6%, mean 0.6%) and trilete spores (0%–3.7%, mean 1.7%) also occurred. Zone D (10 samples, 12.9–11.6 ka) Shrub and herb pollen (60.2%–69.3%, mean 63.9%) showed relatively little variation in zone D and was dominated by Artemisia (14.9%–23.9%, 19.3%), Apiaceae (7.1%–16.6%, mean 11.5%), and Compositae (4.0%–21.6%, mean 10.6%). Intriguingly, the mean value of Compositae in

this zone was the highest of the entire section. In contrast, hydrophilous herb pollen (5.6%– 15.6%, mean 9.3%) showed the lowest mean value of the section. The abundance of Cyperaceae pollen varied between 0% and 12.0%, with the lowest mean value (4.1%) of the entire section. Poaceae (0%–3.1%, mean 0.9%), Polygonum (0%–2.1%, mean 0.3%), Myriophyllum (0.5%– 6.0%, mean 2.8%), and Typha (0%–3.1%, mean 1.2%) were regularly present in this zone. Che- nopodiaceae (0.5%–3.8%, mean 2.0%), Ranunculaceae (0%–5.2%, mean 2.1%), Caryophylla- ceae (0%–2.5%, mean 1.1%), and Ephedra (0%–2.5%, mean 1.2%) were present throughout, but at low abundances (< 2%). Other taxa occurred sporadically, including Caprifoliaceae, Thalictrum, Lamiaceae, and Spiraeoideae. Relative to zone C, broad-leaved pollen in this zone (17.7%–34.0%, mean 26.3%) showed a slight decrease and were dominated by Quercus (7.3%–15.0%, mean 11.0%), Castanea (5.2%– 11.7%, mean 8.4%), and Betula (2.1%–9.1%, mean 4.9%). Ulmus (0%–4.0%, mean 1.6%) and Corylus (0%–3.6%, mean 1.5%) pollen were present throughout the zone, although at low abundances. Liquidambar and Juglans occurred sporadically. Conifer pollen (5.1%–13.5%, mean 9.4%), dominated by Pinus (4.1%–13.0%, mean 8.4%), showed an increase in this zone. Picea and Abies pollen were locally present. The abundance of fern spores and algae varied between 6.6% and 14.3% with a mean of 10.8%, and were dominated by Pediastrum (2.7%–8.5%, mean 5.1%) and monolete spores (0.9%–4.9%, mean 2.7%). Trilete spores (0%–3.3%, mean 2.1%) were present and Concentri-

cystis occurred sporadically [Fig 3]. Zone E (8 samples, 11.6–10.6 ka) Shrub and herb pollen (49.5%–68.6%, mean 59.4%) decreased slightly in zone E relative to zone D. Artemisia (12.0%–21.4%, mean 17.0%), Apiaceae (0.5%–17.1%, mean 9.3%), Compo- sitae (2.1%–10.0%, mean 5.6%), and hydrophilous herb pollen (8.6%–18.0%, mean 11.9%) were the main components. Cyperaceae (2.9%–11.0%, mean 5.9%) was the dominant hydro- philous herb, along with minor Poaceae (1.0%–3.3%, mean 2.1%), Myriophyllum (0.9%–5.0%, PLOS ONE Last deglacial pollen reocord from the eastern TP PLOS ONE | https://doi.org/10.1371/journal.pone.0232803 May 6, 2020 7 / 12